This means that we need to find a number plus 9 equals 9, and another number minus 9 equals 9. Suppose the number is 9 and the addition is a+ 9=9, then A is the number we are looking for. Suppose the number is 9 and the subtraction is b-9=9, then B is also the number we are looking for. According to the topic, we can establish the following equations: a+9=9, b-9=9.
Now let's solve this system of equations and find the values of a and b, and the calculation results are: a=0, b= 18. So the addition of 9 is 0+9=9, and the subtraction of 9 is 18-9=9.
Other related
Mathematics [English: Mathematics, from ancient Greece μ? θξμα(máthēma)； Often abbreviated as math or maths], it is a discipline that studies concepts such as quantity, structure, change, space and information.
Mathematics is a universal means for human beings to strictly describe and deduce the abstract structure and mode of things, and can be applied to any problem in the real world. All mathematical objects are artificially defined in essence. In this sense, mathematics belongs to formal science, not natural science. Different mathematicians and philosophers have a series of views on the exact scope and definition of mathematics.
Mathematics plays an irreplaceable role in the development of human history and social life, and it is also an indispensable basic tool for studying and studying modern science and technology.
Development history
Mathematics (hanyu pinyin: shùXué；; ; Greek: μ α θ η μ α κ; English: mathematics or maths), whose English comes from the ancient Greek word μθξμα(máthēma), has the meaning of learning, learning and science. Ancient Greek scholars regarded it as the starting point of philosophy and the "foundation of learning". In addition, there is a narrow and technical meaning-"mathematical research". Even in its etymology, its adjective meaning is used to refer to mathematics whenever it is related to learning.
Its plural form in English and plural form in French plus -es form mathématiques, which can be traced back to the Latin neutral plural (mathematica), and Cicero from the Greek plural τ α μ α θ ι α ι κ? (ta mathē matiká).